/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingOperators/Public/CompositionOps/CubeGridBooleanOp.h
Optional: information to weld corners along the Z axis to create ramps/pyramids/pyramid cutaways.
struct FCornerInfo
bool[4]
WeldedAtBase
"Base" refers to the 0-3 indexed corners in FOrientedBox3d, and the flags here are true if the vertex is welded to its Z axis neighbor.